Thermal stability of RuO2-based bottom electrodes during various ambient annealings

Abstract

RuO2 thin films were prepared on SiO2/Si, TiN/SiO2/Si and Ru/poly-Si by using DC magnetron sputtering. The annealing of the RuO2-based bottom electrodes was performed in oxygen and argon ambients and in high vacuum in the temperature range of 400 degrees C similar to 800 degrees C. In oxygen-ambient annealing, the surface morphology was drastically changed due to the evaporation of ruthenium dioxides in the form of RuO3 and RuO4. The RuO2 thin film annealed in high vacuum was reduced to the Ru metal phase. Evaporation and reduction of the RuO2 thin films could actually be observed during the deposition of (Ba,Sr)TiO3 thin films. Oxygen diffusion through the RuO2/diffusion barrier/poly-Si structures is also discussed.